Computerized tomography makes use of rays to scan a certain part of a human body taken from a cross section with a certain thickness, and reconstructs cross-sectional images by a computer according to different absorption capacities of different human tissues for rays. During a process for performing a computerized tomography scanning and a reconstruction by using X-rays, the X-rays generated by a ball tube have a certain spectral width, and the X-ray absorption coefficient of a scanning subject decreases as the X-ray energy increases. After the X-rays with continuous energy spectrum pass through a scanning subject, such as a human body, low-energy rays are easily absorbed, high-energy rays are easy to pass through, and the average energy of the rays becomes high and the rays gradually harden. The effect is called as the beam hardening effect. The beam hardening effect may cause artifacts during image reconstruction and affect the quality of the image reconstruction.